Such a device and such a process are known from DE 198 08 590 A1. The prior-art device is especially a respiration moistener. The prior-art respiration moistener has a breathing gas line with a gas inlet, into which the incoming gas to be moistened can be fed, and a gas outlet, from which the moistened breathing gas is removed. The device has, furthermore, an evaporating device, into which a liquid to be evaporated can be fed. The liquid fed is sent by a dispensing pump to an evaporator, which evaporates the liquid to be evaporated and which feeds the vapor generated into the breathing gas flowing in the breathing gas line. The evaporating device is connected to a control device, which sets the outlet temperature and the outlet moisture of the breathing gas flowing out of the gas outlet. The outlet temperature and the outlet moisture can be regulated independently from each other. The evaporating device may comprise, for example, a dispensing pump, which delivers a quantity of liquid proportional to the volume flow of the breathing gas through the breathing gas line to an evaporating unit. The outlet temperature of the outgoing gas can then be set independently from the fed quantity of liquid by regulating the temperature of the evaporating unit such that the vapor generated by the evaporator reaches a certain temperature and a mixture of breathing gas and vapor, which mixture has the desired outlet temperature, is obtained.
It should however be borne in mind in this context that the temperature of the vapor cannot be below the boiling point of the liquid. In addition, there are hygienic specifications, which require a vapor temperature above the boiling point of the liquid. This may cause the development of an excessively high outlet temperature at the gas outlet of the device when the inlet temperature assumes excessively high values. This may happen, for example, when the breathing gas is fed to the gas inlet of the respiration moistener by means of a fan or another pumping device.